The present disclosure relates to a capacitive type touch input device for a user input, and more particularly, to a technology to have a structure for adjusting sensitivity to a touch input.
When there is an object, such as a human being's finger, near a conductor (=electrode), capacitive capacitance is formed between the conductor and the finger. The capacitive capacitance may provide a current path between the conductor and the finger. The size of the capacitive capacitance may vary according to the distance between the conductor and the finger.
The capacitive type touch input device is a device that uses the above-described principle to dispose a plurality of conductors on the surface of a touch panel in the touch input device, and detect that the size of a current flowing through a specific conductor varies when there is a finger near the specific conductor, in order to detect whether a touch input has been applied. Thus, the capacitive type touch input device may include a touch input detector (=touch input detection circuit unit, touch input detection part) for measuring the size of the current. The capacitive type touch input device may function as a component of a user device, such as a smart phone.
When it is assumed that a touch input is not applied to a target conductor to be determined on whether a touch input is not applied thereto, the target conductor may have certain reference capacitance. The reference capacitance may be mutual capacitance that is formed between the target conductor and another conductor, and stray capacitance that is formed between the target conductor and other circuit devices. In this case, the mutual capacitance may be intentionally formed according to design intention and the stray capacitance may be a capacitance component that occurs unintentionally. When a finger is in contact with the target conductor, the capacitance of the target conductor may have a changed capacitance value that is different from the reference capacitance. In this case, it is possible to determine the sensitivity of a touch input detector according to the ratio of a variation in capacitance that occurs due to contact and the reference capacitance. If the size of the reference capacitance is too large, it may be difficult to detect whether the capacitance formed at the target conductor varies by a touch input. Thus, the reference capacitance needs to have an appropriate value.
However, since as described above, the reference capacitance may include unintended stray capacitance, there is a limitation in that the reference capacitance may be larger than design intention.
Also, in a capacitive type touch input device in which a plurality of conductors is disposed, uncontrollable mutual capacitance may also be formed between the plurality of conductors. From the point of the touch input detector, the uncontrollable mutual capacitance may configure the above-described stray capacitance.